Objective: Serum vitamin D is shown to be decreased and associated with higher thyroid volumes in Graves disease (GD). We aimed to investigate the relationship between thyroid volume and baseline serum vitamin D status in newly diagnosed GD patients.

Methods: This was a single-center cross-sectional study with a total of 61 new-onset GD patients (n=61, F: 40, M: 21) who were divided into two groups, according to baseline serum vitamin D levels, as Group-1 (vitamin D <20; n: 42) and Group-2 (vitamin D ≥20; n=19). Thyroid volume (mL) and isthmus measurements (mm) were compared between the two groups.

Conclusion: Baseline serum vitamin D levels are inversely related with thyroid volumes, fT3, and TRAb levels in new-onset GD. In addition to several advantages, optimization of vitamin D levels would also be beneficial in the surveillance of these patients. However, larger scale studies are required to make further suggestions.